<template>
  <view>
    <view class="scroll-view-container">
      <!-- 左侧的滚动视图区域 -->
      <scroll-view class="left-scroll-view" scroll-y :style="{ height: wh + 'px' }">
        <block v-for="(item, index) in cateList" :key="index">
          <view :class="['left-scroll-view-item', index === active ? 'active' : '']" @click="activeChanged(index)">{{ item.cat_name }}</view>
        </block>
      </scroll-view>
      <!-- 右侧的滚动视图区域 -->
      <scroll-view class="right-scroll-view" scroll-y :style="{ height: wh + 'px' }" :scroll-top="scrollTop">
        <view class="cate-lv2" v-for="(itemR, indexR) in cateRightList" :key="indexR">
          <view class="cate-lv2-title">{{ itemR.cat_name }}</view>
          <view class="cate-lv3-list">
            <!-- 三级分类-->
            <view class="cate-lv3-item" v-for="(itemT, indexT) in itemR.children" :key="indexT" @click="gotoGoodsList(itemT)">
              <!-- 图片 -->
              <image :src="itemT.cat_icon"></image>
              <!-- 文本 -->
              <text>{{ itemT.cat_name }}</text>
            </view>
          </view>
        </view>
      </scroll-view>
    </view>
  </view>
</template>

<script>
export default {
  data() {
    return {
      // 窗口的可用高度
      wh: 0,
      // 分类数据列表
      cateList: [],
      // 二级分类列表
      cateRightList: [],
      // 当前选中项的索引，默认为0
      active: 0,
      // 滚动条距离顶部的距离
      scrollTop: 0
    };
  },
  onLoad() {
    // 获取当前系统的信息
    const systemInfo = uni.getSystemInfoSync();
    // console.log(systemInfo);
    this.wh = systemInfo.windowHeight;
    this.getCateList();
  },
  methods: {
    async getCateList() {
      const res = await uni.$http.get('/categories');
      console.log(res);
      if (res.data.meta.status !== 200) return uni.$showMsg();
      this.cateList = res.data.message;
      this.cateRightList = res.data.message[0].children;
    },
    activeChanged(i) {
      this.active = i;
      this.cateRightList = this.cateList[i].children;
      this.scrollTop = this.scrollTop === 0 ? 1 : 0;
    },
    gotoGoodsList(i) {
      uni.navigateTo({
        url: '/subpkg/goods_list/goods_list?cid=' + i.cat_id
      });
    }
  }
};
</script>

<style lang="scss">
.scroll-view-container {
  display: flex;

  .left-scroll-view {
    width: 120px;

    .left-scroll-view-item {
      line-height: 60px;
      background-color: #f7f7f7;
      text-align: center;
      font-size: 12px;

      // 激活项的样式
      &.active {
        background-color: #ffffff;
        position: relative;

        // 渲染激活项左侧的红色指示边线
        &::before {
          content: ' ';
          display: block;
          width: 3px;
          height: 30px;
          background-color: #c00000;
          position: absolute;
          left: 0;
          top: 50%;
          transform: translateY(-50%);
        }
      }
    }
  }
}
.cate-lv2-title {
  font-size: 12px;
  font-weight: bold;
  text-align: center;
  padding: 15px 0;
}
.cate-lv3-list {
  display: flex;
  flex-wrap: wrap;

  .cate-lv3-item {
    width: 33.33%;
    margin-bottom: 10px;
    display: flex;
    flex-direction: column;
    align-items: center;

    image {
      width: 60px;
      height: 60px;
    }

    text {
      font-size: 12px;
    }
  }
}
</style>
